It depends on where you live. In the U.S. in most states, there is no specified limit. In Tennessee where I live, "handgun" is basically defined as any gun designed to be fired with one hand or something very close to that.
To legally purchase or own a handgun, you must be 21.
It depends on what the crime is that is on your record. If it is a felony, you can't legally own a handgun anywhere in the U.S.
If you have a handgun carry permit, definitely. The handgun carry permit covers "any handgun that you legally own or posses."
To legally own a long gun (rifle or shotgun) in Tennessee, you must be 18. To legally own a handgun in Tennessee, you must be 21.
Generally speaking, no. If you have a felony, you cannot legally own or purchase a gun.
Generally speaking, no. A felon cannot own or even possess a handgun legally. The exception to that is if the felon has had his rights restored.
Many gun dealers do take firearms in trade. It is up to the individual dealer. However, you must be able to legally own a handgun to do that.
It depends on whether you mean legally, or what is the biggest handgun available, and whether you mean handgun size, or caliber size. The largest commonly available caliber is .45 ACP, however, .50 AE is also fairly common. That said though, there is also a handgun available in .600 NE. Most states don't have restrictions on caliber, however, some may.
It depends. A simple expungement does not qualify you to own a handgun. If have been charged with something that disqualifies you from owning a gun, you have to have your rights restored before you can legally buy one again.
In most U.S. states, there is no specific minimum age to use a gun for legal purposes, but a person does have to be 21 to legally own or purchase a handgun.
Yes, if you can otherwise legally purchase a handgun, there is no requirement to have a social security number.
By federal law, yes. Federal law prohibits "Undocumented immigrants."